In construction, modular surface systems are commonly employed in order to reduce costs and construction time associated with building floors, walls and ceilings. A typical example of such a modular system is a suspended ceiling, incorporated within many professional and office environments, standardly comprised of a plastic or metal grid defining square/rectangular recesses, these filled with tessellating panels or tiles spanning the ceiling, and often interspaced at regular points with dedicated luminaire lighting panels.
Traditionally such lighting panels utilise one or more fluorescent tubes in combination with light redirecting reflectors. However, increasingly, solid state lighting elements, such as LEDs, are being used in lighting panel applications as an alternative to fluorescent tubes. LEDs carry numerous general advantages compared with traditional (fluorescent or incandescent) light sources including long lifetime, high lumen efficiency, low operating voltage and fast modulation of lumen output. Additionally, in office environments it is generally desired that modular systems incorporate acoustic dampening elements in order to mitigate the transmission of sound across large open spaces. In particular, it is often desirable that lighting panels themselves incorporate acoustically absorbing tiles or layers, such that comparatively large portions of the total ceiling surface area may be provided with lighting, without compromising on acoustic dampening.
Hence LED modular lighting panels carry numerous advantages compared with fluorescent panels. However, in contrast to a tubular lighting element, an individual LED package is able to generate light emission across only a very narrow output area. Hence a plurality of LEDs are typically utilised within such devices, for example arranged in arrays beneath a reflector, the reflector adapted to redirect emitted light across an output window located at the base of the panel.
WO 2013/190447 for example discloses a modular lighting device comprising an acoustically absorbing tile, several rows of LED elements and a reflector arrangement.
WO 2014/187788 discloses a light-emitting acoustic panel that may be mounted in a ceiling. The light-emitting acoustic panel comprises a sound-absorbing layer and a light-transmissive layer arranged in parallel such that a space is formed in-between. In the space a light source and a reflector are arranged such that light emitted by the light source is redirected by the reflector and emitted towards a reflective side of the sound-absorbing layer. The light source is an elongated light source that is arranged along a line that is parallel to an edge of the light-emitting acoustic panel, wherein the elongated light source comprises a plurality of LED elements.
Known LED lighting panels have the disadvantage that it is difficult to achieve large lateral sizes, for example greater than approximately 60×60 cm, while maintaining an homogeneous light distribution, in order to avoid brighter and darker spots occurring at various points across the width of the window. Such non-uniformity of light intensity is aesthetically unsatisfying as well as functionally inefficient.
It is particularly difficult to avoid this non-uniformity with panels that also incorporate acoustic functionality.
Desired therefore is a lighting panel utilising strips of solid state lighting elements, and able to incorporate an acoustically absorptive tile layer but wherein the intensity distribution of light generated across the width of the panel area exhibits improved uniformity, even for panels of large lateral size.